Turbochargers for diesel and gasoline engines are well known. It has been found that under certain operating conditions, the use of a turbocharger improves overall engine efficiency and provides increased power. However, when the turbocharger is not functioning properly, turbine efficiency may be lowered, the engine may operate in an unstable manner and, in extreme cases, engine damage may result. Engine designers have therefore been particularly interested in closely monitoring the operation of the turbocharger in an effort to identify problems before they impact engine performance. A boost pressure leak is one such problem in a turbocharged engine.
A turbocharger may typically have one or more pairs of turbines and compressors. The turbines are driven by engine exhaust gas and they, in turn, drive one or more compressors in order to increase the pressure of intake air provided to the engine. The amount of pressure above normal atmospheric pressure that the compressor of the turbocharger generates may typically be referred to as “boost.” Loss of boost pressure in a turbocharged engine may typically be referred to as a boost leak. A turbocharger configured to electronically control the compressor to maintain a desired intake manifold pressure will respond to a boost leak by increasing the turbospeed. Because high turbospeed can cause failure of the turbocharger, the consequences of a boost leak may prove catastrophic for the turbocharger.
It is known to evaluate boost pressure using sensors indicative of the pressure of air entering a turbocharger compressor inlet. One such example is U.S. Pat. No. 6,698,203 (the '203 patent) issued to Wang on Mar. 2, 2004. The '203 patent discloses a system for estimating absolute boost pressure in a turbocharged internal combustion engine using the temperature and pressure of air entering the turbocharger compressor, the rotational speed of the turbine, and the rotational speed of the engine.
Although the system of the '203 patent may provide a method for estimating the absolute boost pressure using known or calculated values, the system does not take into account an engine system having auxiliary components or devices that receive a portion of the compressed air from the compressor. Thus, the system of the '203 patent only takes into account compressed air flowing to the intake manifold and not compressed air flowing to auxiliary components or devices, thereby resulting in less accurate calculations. These less accurate calculations may put the engine and turbocharger systems at risk of damage.
The disclosed system is directed to overcoming one or more of the problems set forth above.